SAPROPHYTISM AND SYMBIOSIS 757 



the possibility of complete autophytism than its actual existence. The 

 autophytic bacteria (p. 526) also are capable of living saprophytically, 

 and hence are representative mixophytes. 



Saprophytism in the seed plants. — The views of botanists as to sapro- 

 phytism in the seed plants often have been altered, and even now the 

 paucity of experimental data makes anything like a definite statement 

 quite impossible. The first view was that all plants without chlorophyll 

 are parasites. When it was discovered that the roots of Monotropa (fig. 

 1 104) are not connected with the roots of green plants, the term sapro- 

 phyte was used to distinguish such plants from true parasites, which always 

 are attached to other plants. Afterward it was discovered that the roots 

 of Monotropa usually are completely enveloped by fungi, which act in an 

 intermediary capacity between the seed plant and the humus, so that 

 once more Monotropa is, perhaps, to be regarded as parasitic, though 

 on fungi rather than on roots (see also p. 792). Similarly, all of the 

 higher plants (except possibly the West Indian orchid, WuUschlaegelia) 

 that commonly have been regarded as saprophytic, such as Corallorhiza 

 and many other orchids, and such as the gametophytes of Lycopodium 

 and Botrychium (fig. 1108), have symbiotic relations with fungi and 

 probably are parasitic rather than saprophytic; however, in such 

 orchids as Corallorhiza partial saprophytism still seems a possibility, 

 especially since the fungi occur within the root. The term symbiotic 

 saprophytism has been applied to this phenomenon to express the 

 double relationship, namely, the symbiotic relation between the fungus 

 and the higher plant, and the saprophytic relation between the fungus 

 and the soil (see further, p. 798). 



While the supposedly saprophytic seed plants and pteridophytes ap- 

 pear, in reality, to be parasites, a capacity for saprophytism has been 

 found to exist in various ordinary green plants. Long ago it was sup- 

 posed that the luxuriant development of plants in humus is due to the 

 absorption of organic food, but later this view was abandoned, the luxu- 

 riance being referred to various factors, such as the high water content, 

 the abundance of nitrates, and the beneficial activities of earthworms, 

 fungi, and bacteria. However, it has been discovered that when maize 

 is grown in glucose or in invert sugar with its leaves in air which is de- 

 void of carbon dioxid, sugar is absorbed by the root hairs and is utilized 

 directly in the manufacture of starch. In such an experiment the maize 

 behaves as a holosaprophyte, and it may be a partial saprophyte in ordi- 

 nary cultivation, although the roots appear to absorb very little organic 



